The present invention relates to a cleaning apparatus for an object lens, and more particularly to a cleaning apparatus for an object lens used for gathering a laser beam in an optical disk apparatus.
Generally, in an optical disk apparatus, a laser beam is irradiated onto a surface of a disk through an object lens so that the laser beam is gathered into a spot having a diameter of approximately 1 .mu.m, and information is reproduced by utilizing a reflection of the laser beam. A laser beam reflected by the disk is incident upon an optical processing system through the object lens. In such a system, when dust is accumulated or adhesive material is attached to the object lens, an amount of beam transmitted in the object lens is decreased. Additionally, a beam spot on a focus point may be distorted or blurred. As a result, a laser is not focused, and thus a tracking servo system may not function normally. This causes an occurrence of a problem in that errors frequently occur in a reproducing operation.
In order to eliminate the above-mentioned problem, eliminating the dirt on the object lens is effective. However, it is difficult for a user to disassemble an optical disk apparatus to clean off an object lens. Cleaning apparatuses are supplied for cleaning off a surface of an object lens by inserting them into a disk loading part in the same manner as an usual optical disk.
A description will now be given of conventional supporting mechanisms of an object lens. FIG. 1A shows a wire suspension type supporting mechanism, and FIG. 1B shows a shaft sliding type supporting mechanism. In FIGS. 1A and 1B, a focusing direction, that is, a direction of a rotational axis of an optical disk loaded in an optical disk apparatus is indicated by an arrow FO, a tracking direction, that is, a radial direction of the optical disk is indicated by an arrow TR, and a tangential direction of the optical disk is indicated by an arrow TA. It is understood that the focusing direction is perpendicular to a surface of the optical disk. The tracking direction is perpendicular to the surface of the optical disk. The tangential direction is tangential to a track formed on the optical disk. The focusing direction FO is perpendicular to both the tracking direction TR and the tangential direction TA.
In the supporting mechanism shown in FIG. 1A, a holder 11 provided with an object lens 10 is attached to a base 12 fixed on a portion of a head carriage (not shown in the figure) via four suspension wires 21. The suspension wire enables the holder 11 to be elastically supported in the tracking direction TR and the focusing direction FO. Additionally, the holder 11 is driven by an actuator including coils and magnets, and is movable in the tracking direction TR and the focusing direction FO.
In the supporting mechanism shown in FIG. 1B, a holder 11 provided with an object lens 10 is elastically supported by two elastic members 22. A shaft 31 extended in the focusing direction FO penetrates through the center of the holder 11. A bearing 32 is provided on the holder 11 to slide along the shaft 31. Either end 22a of each of the elastic members 22 and one end of the shaft 31 are fixed to a head carriage (not shown in the figure). The holder 11 is driven by an actuator (not shown in the figure) similarly to the mechanism shown in FIG. 1A so as to be movable in the focusing direction and a rotational direction with respect to the shaft 31.
It should be noted that the focusing of the object lens 10 onto a surface of an optical disk is performed by the movement of the holder 11 in the focusing direction FO, and a laser spot is accurately positioned on a track formed on the optical disk by the movement of the holder 11 in the tracking direction TR or the rotational direction with respect to the shaft 31.
A description will now be given of a conventional cleaning method for an object lens. The conventional cleaning apparatus cleans off dust accumulated on a surface of an object lens by means of a brush (or a pad). That is, the brush makes contact with a surface of an object lens and is slid on the surface of the object lens.
In either type of the above-mentioned supporting mechanism for an object lens, the holder 11 provided with the object lens is movable in the tracking direction TR. Accordingly, if a sliding direction of a brush corresponds to the tracking direction, which is a movable direction by an actuator, the object lens is moved by a sliding force exerted by the brush, and thus there is a problem in that an effective cleaning cannot be performed.
Additionally, if the sliding direction of the brush corresponds to the tangential direction TA which is perpendicular to the tracking direction TR in the supporting mechanism shown in FIG. 1A, an excessive load is applied to the wires 21 in a longitudinal direction thereof. In such a case, there is a possibility that a deformation of the wires 21 or an exfoliation of adhesion applied for fixing the wires 21 occurs. Additionally, in the case the supporting mechanism shown in FIG. 1B is used, dust on the surface of the object lens flies in a direction where the shaft 31 is located and the dust is trapped in a space between the shaft 31 and the bearing 32; results in rough slide or rotation of the holder 11 and thus there is a problem that a stable control of the movement of the holder 11 is not achieved.